That's according to Jamie Carragher, who attempted to explain Mourinho's reasons for targeting the Chilean in the January transfer window.

Sanchez looked set to head to Manchester City, where he was to link back up with Pep Guardiola, who managed him at Barcelona.

But the Citizens are now out of the running for the 29-year-old after the Red Devils made it clear they are willing to stump up the £35million Arsenal want for the forward - something City are unprepared to do.

Jamie Carragher believes Jose Mourinho has run out of patience with Anthony Martial

Mourinho's move for the Chilean is a little out of the blue, much like his successful swoop for Romelu Lukaku ahead of the season.

And Carragher believes it is Martial's form that has prompted the Red Devils boss to take evasive action this January and sign the player from under Manchester City's nose.

The France international got on the scoresheet in Man United's win over Stoke (Image: AFP)

"So often you say you want more from Martial and you see the ability and the quality he has," said Carragher on Sky Sports.

"If anyone in this team is under more pressure with the news of Alexis Sanchez supposedly coming... it's possibly, not the end, he'll still be part of the squad but you think it's going to be difficult for him going forward if Sanchez came.

Mourinho is keen on signing Alexis Sanchez in the January transfer window (Image: REUTERS)

"This is a player who came to Manchester United a couple of years ago and you were thinking he was going to be a world beater.

"It just hasn't happened and I think Jose Mourinho has probably ran out of patience. That's why he's come out of nowhere to try and get Sanchez who's come on the market. He's saying I want more from this player and it's not enough."